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Full text of "Blackleg"

UNIVERSITY OF CALIFORNIA Agricultural Experiment Station 

College of Agriculture e. w. hilgard, director 

BERKELEY, CALIFORNIA 



CIRCULAR No. 2. 

(May, 1903.) 



BLACKLEG 

By ARCHIBALD R. WARD, 
Veterinarian and Bacteriologist. 



Synonyms. — Blackleg is also known as Symptomatic Anthrax, Em- 
physematous Anthrax, Quarter 111, Black Quarter, and Rauschbrand. 

Animals Affected. — For all practical purposes the disease may be con- 
sidered as merely one of cattle, occurring chiefly among young stock 
between the ages of three months and four years. Cattle under three 
months are naturally immune, and for the same reason animals over 
four years but rarely are attacked. It is a matter of common observa- 
tion that calves in good condition are more liable to attack than poorer 
ones. Nevertheless, it is not safe to consider that poor condition will 
confer immunity against blackleg. The disease is not communicable 
to man. 

Symptoms. — The most important symptom is the occurrence of swell- 
ings under the skin on any part of the body except on the legs below 
the knees or hocks. The swellings when first appearing are painful, but 
as they become larger the skin in the center of the swelling becomes 
insensible. The enlargements are, to a large extent, composed of gas 
bubbles imprisoned in the loose tissues beneath the skin, and the large 
ones, when pressed, give forth a very characteristic crackling sound. 
When a swelling is tapped with the finger, it emits a drum-like resonance. 
When occurring upon the legs, the tumors may cause lameness and 
even prevent the victim from walking at all. If the tumor is cut open, 
black or frothy blood runs out. Fever is present and is manifested by 
the usual indications, such as quickened breathing, dullness, and loss 
of appetite. Death occurs within a period varying from eight hours to 
two days after the beginning of the attack. 

Changes Observed After Death. — The carcass bloats rapidly and like 
wise decomposes quickly after death. When swellings are cut open they 
are found to contain more or less clotted black blood and gas. The 



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excessive blackening by blood gives rise to the various names, such as 
black quarter and blackleg. Some internal organs are more or less 
affected, but the changes in the internal organs need not be considered 
in recognizing the disease. 

Cause. — The disease is brought about by bacteria which live naturally 
in the soil and which gain access to the body through wounds, and more 
rarely with food eaten. The germs of blackleg are quite generally dis- 
tributed, but certain soils have been observed to offer particularly 
favorable conditions for their existence, and in consequence are especially 
dangerous for stock pastured thereon. Among these are damp or water- 
logged soils, or heavy clay soils. Punctured wounds, such as those 
produced by barbed wire, briers, stubble, etc., are regarded as fruitful 
sources of infection. A diseased animal is not regarded as a direct 
source of danger to other animals in contact with it. If the swellings 
have been cut open and blood is discharged, there is more danger. 

Disposal of the Dead. — Burning is preferable to any other method of 
disposal, as it is the only means that can be relied upon to absolutely 
destroy all germs of the disease with which the carcass is teeming. 
When the victim is buried the germs will remain alive in the soil long 
after the carcass has decomposed, and will constitute a menace to the 
health of stock pastured upon the land. Earthworms are said to 
convey infection to the surface. 

Treatment Useless. — No successful treatment is known, and even should 
a remedy be discovered, its usefulness would be limited, owing to the 
rapidly fatal nature of the affection. Cutting open the swellings and 
injecting various medicines has seldom met with success. Excessive 
exercise and bleeding have also been found next to useless. 

Prevention by Vaccination. — The method is based upon the principle 
that an attack of the disease may be warded off by purposely causing 
the animal to have an exceedingly mild attack by artificial means. 
Vaccine is prepared by obtaining flesh from a diseased animal, finely 
dividing it and subjecting it to a high temperature for several hours. 
This treatment of the diseased material reduces the disease-producing 
power of the blackleg germs that it contains. The vaccine material, 
when injected under the hide of a healthy calf, produces little or no 
visible effect upon the health, but experience shows that this vaccina- 
tion protects the animal from catching the disease naturally for a year 
or more. The method was originated in Europe in 1883, and has since 
been improved upon and used in all districts of the civilized world 
where stock-raising is carried on extensively. Vaccination as a pre- 
ventive of blackleg has been and is encouraged by the Bureau of 
Animal Industry of the United States Department of Agriculture and 



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the Agricultural Experiment Stations in the various States. Its use has 
long since passed the uncertain experimental stage. 

When Not to Vaccinate. — Calves should not be vaccinated unless it is 
known that the disease has previously occurred among animals pastured 
on the same land. When vaccination is practiced there is great risk of 
introducing the germs of the disease and thus infecting the land, which 
would necessitate vaccinating annually thereafter. A stock owner can 
much better afford to ascertain that his range is infected by waiting 
until a death has occurred, than to rush into vaccinating before he is 
certain that it is necessary. Blackleg does not sweep over a region rapidly 
like some infectious diseases. Do not castrate or dehorn at the time 
of vaccination. Do not vaccinate animals already stricken with the 
disease. ' 

What Animals to Vaccinate. — Animals between the ages of five months 
and two years should be vaccinated several weeks before the disease 
usually appears. Animals older or younger occasionally die of the 
disease, but it is not profitable to vaccinate against these attacks, for they 
occur rarely. If animals under six months are vaccinated, the process 
should be repeated the following year. The operation is facilitated by 
confining the calves in a chute. 

Where Vaccine May Be Obtained. — The Bureau of Animal Industry, 
United States Department of Agriculture, Washington, D. C, furnishes 
vaccine free to all applicants. Each stock owner must apply directly 
to Dr. D. E. Salmon, the Chief of the Bureau of Animal Industry, and 
an application blank will be mailed to him, upon which the owner shall 
indicate the amount needed, etc. Under no circumstances will blackleg 
vaccine be sent to any one person for distribution to others, or for use 
upon other cattle than his own. For administering the vaccine, a vac- 
cinating outfit must be obtained, costing from $4 to $6. The outfit can 
usually be readily obtained through drug stores. Vaccine prepared by 
private firms can be purchased from the druggist or directly from the 
addresses below. Firms preparing vaccine, known to the writer, are: 
The H. K. Mulford Co., represented by Thomas G. Finley, 41 Stevenson 
street, San Francisco; The Cutter Analytic Laboratory, Rialto Build- 
ing, San Francisco; The Pasteur Vaccine Co., represented by Cadogan 
& McClure, 110 Jessie street, San Francisco; Parke, Davis Co., Detroit, 
Michigan. The various manufacturers supply vaccinating outfits and 
furnish plainly worded directions for use.